It is known to screen print frit patterns on glass substrates, e.g., in connection with decorative bands, solar control “dot” patterns, etc. Screen printed articles may be laminated to other substrates and used in, for example, automotive applications such as windshields. A screen printed article also may be connected to another substrate and used to form an insulated glass unit (IG unit or IGU). Inkjet printing has been used an alternative to screen printing.
In this vein, FIG. 1 schematically demonstrates a process conventionally used in forming an IGU with a screen printed coated article. A stock glass sheet is provided in step S102. The stock sheet is cut to size in step S104, and frit material in the desired pattern(s) is/are silkscreen or inkjet printed on the substrate in step S106. In step S108, a high temperature heat treatment (HT) operation such as heat strengthening and/or thermal tempering is carried out, which also in some cases helps to cure the frit material that is silkscreen or inkjet printed on the substrate and/or to fuse it to the substrate. A thin film layer stack optionally is formed over the patterned layer in step S110, e.g., to form a low emissivity (low-E), antireflective (AR), and/or other functional coating. The thin film layer stack may be formed via sputtering and/or the like. The coated article that includes the substrate with the printed pattern and the thin film layer(s) thereon may be built into an IG unit in step S112, e.g., by providing a second substrate and maintaining the second substrate and the coated article in substantially parallel spaced apart relation to one another using a spacer and an edge seal provided around a peripheral area of one or both of the substrates. In this example, ceramic frit patterns may be provided on interior and/or exterior glass surfaces of the substrate. When low-E coatings are provided, they typically are oriented on an interior facing surface of the substrate.
The ceramic frit materials typically used in conventional processes require high temperatures to form a strong bond with the glass. Temperatures in excess of 500 degrees C., and generally between 500-650 degrees C., are common. This high temperature requirement is convenient in the sense that it allows bonding processes to be performed in connection with the high temperature heat treatment processes associated with heat strengthening and/or thermal tempering, as alluded to above. Indeed, rapid cooling or quenching typically follows the high temperature fusing process, thereby heat treating the article with the pattern thereon. Furthermore, because the sputter or other coating processes happen in post-HT operations, the actual coatings do not necessarily need to be heat treatable.
Unfortunately, however, as is known, HT operations also involve rapid cooling or quenching processes after firing, e.g., to induce stresses in the substrate that “toughen” it, but that effectively prevent cutting, sizing, drilling, and/or other operations. Thus, although there are some efficiency gains in terms of combining frit material curing and/or bonding processes with high temperature HT processes, other efficiency gains cannot be achieved. For example, although it would be desirable to be able to perform HT processes following the blanket coating of the thin film layer stack on a large stock sheet of glass or the like, this currently is not possible because a second high temperature process associated with HT processes that has been separated from frit bonding processes would cause the frit material to re-melt and/or reintroduce stresses in the underlying substrate.
The inventors of the instant application have also observed that thin films disposed on conventional screen and inkjet printed frit patterns sometimes form cracks and/or “pop off” in whole or in part. Cracking can lead to the compromising of the properties of the overlying layer and, for instance, can adversely affect a sheet resistance value and/or IR reflection capabilities, e.g., in the case of a silver-based layer in a low-E coating. It also has been found that conventional ceramic frit materials are not chemically stable and sometimes damage some or all overlying thin film layers.
Thus, it will be appreciated that there is a need in the art for improved heat treatable articles with printed coatings thereon, and/or methods of making the same. For instance, it will be appreciated that it would be desirable to provide an arrangement where it is possible to print or otherwise form a frit or frit-like pattern on a substrate and overcoat a thin film layer stack on the pattern, prior to sizing and heat treatment operations. It also will be appreciated that it would be desirable to provide increased resistance to cracking, better bonding and/or durability of the coating, etc.
In certain example embodiments, a method of making a coated article is provided. A frit material is printed on a major surface of a glass substrate. The glass substrate with the frit material thereon is heated at a first temperature in order to bond the frit material to the glass substrate in a desired pattern. Following the heating, the glass substrate is cooled in a controlled manner that is sufficiently slow to maintain and/or create stress in the glass substrate that is at least similar to those present in the substrate prior to said heating, but fast enough to avoid creating dead annealed glass. Following said cooling, a coating is disposed on the glass substrate and over the desired pattern. The glass substrate is cut to a desired size. The cut glass substrate with the desired pattern and the coating thereon is heat treated at a second temperature in making the coated article, with the pattern having a high gloss before and/or after the heat treating. The second temperature is lower than the first temperature, and/or the frit material undergoes a secondary recrystallization process as a result of the heating.
In certain example embodiments, a method of making a coated article is provided. A coating is disposed on a glass substrate and over a desired frit pattern printed on and bonded to the glass substrate when the glass substrate is in a stress state that permits cutting, with the frit material in the frit pattern having a melting temperature greater than a temperature associated with heat treatment and/or being at least substantially crystalline after having undergone a secondary recrystallization process. The glass substrate is cut to a desired size. The cut glass substrate with the desired frit pattern and the coating thereon is heat treated at a temperature sufficiently high to cause said heat treating but sufficiently low to avoid melting frit material associated with the desired frit pattern in making the coated article.
In certain example embodiments, a method of making a coated article is provided. A frit material is printed on a glass substrate. The glass substrate with the frit material thereon is heated at a first temperature in order to bond the frit material to the glass substrate in a desired pattern. Following the heating, the glass substrate is re-annealed by cooling the glass substrate in a manner that is controlled to be sufficiently slow to maintain and/or create stress in the glass substrate that is the same or similar to that present in the substrate prior to said heating. Following said re-annealing, the glass substrate is forwarded to a fabricator to enable the fabricator to dispose a coating on the glass substrate and over the desired pattern, cut the glass substrate to a desired size, and heat treat at a second temperature the cut glass substrate with the desired pattern and the coating thereon. The second temperature is lower than the first temperature, and/or the frit material undergoes a secondary recrystallization process as a result of the heating.
In certain example embodiments, a large stock glass sheet is provided. A frit pattern is printed on a major surface of the large stock glass sheet, where frit material used in forming the frit pattern has a melting temperature greater than temperatures associated with heat treatment and/or is at least substantially crystalline as a result of having undergone a secondary recrystallization process. A heat treatable thin film coating is provided on the major surface of the large stock glass sheet and over the frit pattern. A stress state of the large stock glass sheet is generally consistent with annealed and/or re-annealed glass and thus permits cutting.
In certain example embodiments, methods of providing insulated glass (IG) units, laminated articles, sized substrates, etc., may be made using these and/or other techniques. Corresponding and/or other products also are envisioned herein.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.